Multi-Stage Forming using Optimized Preform in the Line Array Roll Set Process and Its Industrial Application

The line array roll set (LARS) process was developed to manufacture doubly curved plates for industrial applications. LAPS process deforms a flat plate into a doubly curved plate in a step-wise manner. Forming three-dimensional plates with various curvatures is very challenging, and to obtain highly precise final products, it is necessary to design and appropriately allocate forming increments at each step. In some material processes, formability can be improved by performing multi-stage forming using a preform prior to fabrication of the final shape. In this work, we employed an intermediate shape as a preform for multi-stage forming in the LAPS process in order to fabricate the desired plate with optimal quality. The intermediate shape used in the LARS process is defined by a surface with homogeneous curvature in both the longitudinal and the transverse directions, and therefore, fabrication can be achieved without complicated controls of the forming tool. We also developed an approximation method based on a genetic algorithm for designing an intermediate shape of a curved plate. We demonstrated the effectiveness of the proposed method and multi-stage forming methodology through the application of approximated preforms to the manufacture of ship hull plates.